I am working on a large open source project right now via a connection I made on HN. By hanging out in their IRC channel and listening, I've been able to fix a couple of problems before they left the "complaining about it in IRC" stage and percolated up to the "file a bug report" stage. If you're the first to move on it you get to fix it.

My recommendation is find something in open source you use and see if they communicate in IRC or some other open medium. Probably not great universal advice but it has worked for me.

You can't find an undone open source project?

There are no undone open source projects!

They're all undone.

There are always features to add and bugs to fix. Except maybe for TeX.